Chicago Marathon officials announced even more new security tweaks Tuesday in preparation for Sunday's race.

The additional measures have been put in place in response to the Boston Marathon bombings earlier this year. More than 45,000 participants and 1 million spectators will be on the streets.

The Chicago Police Department will enhance their bomb sniffing dog unit with canine units from the Department of Justice and Homeland Security, officials announced Tuesday.

"There are no known threats to Chicago or the marathon at this point," Chicago Police Superintendent Garry McCarthy said Tuesday.

Another change is an old rule that will be enforced more vigorously this year. Spectators will not be allowed to run next to race participants during the race to provide support for any period of time.

On Monday, crews were running cables, hauling dirt, and putting in place the last panels of fencing along Columbus Avenue that will protect parts of Grant Park on Sunday.

"We took some lessons from Boston, which came to backpacks and bomb-sniffing dogs as some of the overt things we'll be doing," Chicago Police Superintendent Garry McCarthy said Monday. "People were very compliant. When we asked them to search their backpacks they said, 'Here.'"

McCarthy says the department will also be relying on cameras and other technology to step up security.

But the Marathon is also making changes, starting with a requirement that runners use clear plastic packs for their gear.

"When our participants come to the starting area, there will be a security screening area, so all those bags will be screened," race director Cary Pinkowski said. "Only our participants, staff and credentialed volunteers will be allowed in those areas."

Another change this year is that each runner must pick up their own race packet, unlike past years when someon could do it for you.

"This is an opportunity to talk to them face to face for the last time. Updates, hopefully on perfect weather, but also any developments we have on race morning that enhances their race experience," Pinkowski said.

All city departments have been put on notice to be ready for anything.

We have to be concerned with the magnitude of the event. We will have a million plus people out on the race course...the weather could change on a dime. There are a hunded and one things we have t o be concerned about to make this a fun and safe event

But what about the 26.2 miles that make up the race course? Police have a plan for that too.

"The covert things you won't see are the undercovers in the crowd. We will have a strong uniformed and undercover presence along the rout in the crowd, because it is an awfully large route to police," McCarthy said.

Most runners told NBC 5 that they understand the reasons for the stepped-up security.

"I think they are going to be pretty good on security. They are going to beef everything up. I read a few things in the paper that said they are going to make sure things like that won't happen," runner Kevin Schnell said.